The present invention relates to a method for generating tooth surfaces of a globoid worm wheel.
Gear cutting of a globoid worm wheel has been conventionally carried out by means of a globoid worm hob (see FIG. 1) or a fly cutting tool which includes a portion of the globoid worm hob. The globoid worm hob includes a thread face whose lead is not constant, in contrast with a cylindrical worm hob. Relieving of a side face extending from a cutting edge of the globoid worm hob has to be performed substantially by manual operation, so that the tooth surfaces of the hob cannot be finished accurately. Also, when a rake face of the hob is re-ground, the tooth profiles of the hob deviates from ideal tooth profiles.
As described above, in the globoid worm hob which has been conventionally employed in a gear-cutting method for the globoid worm wheel, it is substantially difficult to perform the relieving of the side face extending from the cutting edge of the hob so that the globoid worm hob itself cannot be manufactured easily. As a matter of course, it is also difficult to generate highly-accurate tooth surfaces of a globoid worm wheel by using the globoid worm hob.